Feasibility Study Examining the Association between Gut Microbiota and Immune Response to Seasonal Influenza Vaccination in Healthy Adults

Research into the effect of the gut microbiota on host immune response is continuing to shed new light on the underappreciated role of the microbiota in human health. Recent research using mice has shown that the microbiota is critical to the host immune response to influenza infection. Whilst there is great variation in the human gut microbiota, classifications called stool community types can be used to classify individuals based on the abundance of major bacterial taxa.  The primary objective of this study was to investigate the feasibility of using the study protocol for a large randomised controlled trial.  Healthy adult participants (n=125) aged 18 to 64 were recruited from the general population and vaccinated with the seasonal trivalent influenza vaccine. Participants were followed up over a period of six months, during which time, both stool and blood samples were collected. Blood samples were collected at Day Zero, Three, Seven, 28 and 180 to measure immune response. The immune response to vaccination was measured by HAI antibody titres at Day Zero and Day 28. Stool samples were collected at Day Zero and Day 28 to assign participants to one of the four stool community types and assess stability over time. Stool samples were assigned to stool community types using the proportions of major taxa present. The association between stool community type and either post vaccination HAI titre, seroconversion rates or seroprotection rates was also assessed.  The results obtained in this study supported the feasibility of a large randomised controlled trial using the study protocol. The study demonstrated a high participant retention rate (97.6%; 95% CI = 93.1% to 99.5%), as well as high participant adherence to the study protocol and good success obtaining the required blood and stool samples.